function test_dirpath()
{
$this->assertEqual(fs :: dirpath('/wow/test.txt'), fs :: clean_path('/wow'));
$this->assertEqual(fs :: dirpath('wow/hey/test.txt'), fs :: clean_path('wow/hey'));
$this->assertEqual(fs :: dirpath('test.txt'), 'test.txt');
$this->assertEqual(fs :: dirpath('/'), '');
}